Pentax 645 Lens with Fungus- Course of Action?

Just wondering. I may be getting a Pentax FA 120mm lens for a 645 camera and it is being sold with minor fungus spots in it. These are very small its said, as they don't effect picture taking. But never the less, they are in there. How expensive do you think it would cost to have this lens professionally cleaned to get rid of it? Or would it be even worth doing? I've heard just aiming the lens in the sun will kill the fungus, but who knows how long it will stay dormant. Anyway the price is cheap for a FA lens, but just want to weigh my options on this one. There is a chance I may still not get it, but we'll see in a couple days.

The spots aren't actually fungus - they're the waste the fungus leaves behind. You can generally clean them perfectly with plain vinegar and a cotton bud, the tricky part is dismantling the lens without damaging anything and then getting it back together correctly, with no fingerprints and the minimum of dust.

I've cleaned a few Pentax 35mm lenses and had one professionally cleaned, the SMC coatings seem pretty good at resisting it. Get some quotes for having it professionally cleaned and add that to the cost of the lens, if the result is more than a mint example of the same lens then let it pass (unless it's incredibly rare).

The problem shouldn't reoccur providing that you store the lens in a breathable case, use silica gel bags, and make sure the air in the storage area isn't too damp. If you get condensation from sudden temperature changes or the lens gets wet then don't pack it away for a while - I tend to leave my camera on a tripod in the corner of the living room for a few hours where it'll be gently warmed and dried.

I think buying a lens with fungus is only practical if you are going to clean it yourself. If you are planning on sending it off, it might be better to just pass on this one and get one without fungus. I see KEH lists four of those lenses and there are an additional 5 at least, on e-bay.